1. Field of the Invention
The present invention relates to a method for manufacturing a flexible panel and, more particularly, to a method for manufacturing a flexible panel for a flat panel display.
2. Description of Related Art
As one trend in flat panel display technologies is increasing the display areas, a parallel trend is the developments in technical innovations of minimizing weight and thickness. A key one of those developments is to replace the glass substrate with a plastic substrate. However, the device characteristics and film quality made on the plastic substrate are inferior to those made on the glass substrate because the plastic substrate can not resist to the high processing temperature, around 300 to 400 degrees C. Although Sharp Co. has developed a plastic substrate that is capable of withstanding up to approx. 220 degrees C., there is still a need to re-design or modify the conventional FPD process due to the plasticity and flexibility of the plastic substrate.
Seiko Epson Co. has proposed a transfer method, which forms an amorphous silicon layer containing hydrogen (a-Si:H) on a glass substrate, and then forms thin film devices on the surface of the a-Si:H layer, wherein the a-Si:H layer is sandwiched between the thin film devices and the glass substrate. Afterwards, the a-Si:H layer is irradiated with laser light so as to form internal and/or interfacial exfoliation of the a-Si:H layer. Finally, the glass substrate is detached from the a-Si:H layer. However, the energy of the laser light must be controlled precisely so that damage to the thin film devices otherwise caused by the exfoliation is prevented. Besides, such technique is quite difficult and low yield rate.
Whether forming the thin film devices directly on the plastic substrate or using the transfer method, it is necessary to take account of the characteristics of the plastic substrate. Take the thin film transistor for example, a passivation layer, such as a hard coat or a water/air barrier is generally needed to be coated on the surface of a plastic substrate. As for organic thin film transistors (OTFT), the plastic substrate especially needs severe treatments because the organic materials are extremely sensitive to moisture.
Although the plastic substrate is lightweight, thin, and flexible, it has too low a Tg (glass transition temperature) point to withstand high temperature processing, that influences the characteristics of the devices. In addition to that, the problems during the fabrication of thin film devices on the plastic substrate, such as the stress, the static electricity, and the thermal expansion are not easy to be overcome.
Therefore, it is desirable to provide an improved method for manufacturing a flexible panel to mitigate and/or obviate the aforementioned problems.